Effects of windowing the ringdown signal in binary black hole mergers

The ringdown gravitational waves from binary black hole mergers encode information about the remnant black hole and can be used to test of the no-hair theorem. Ringdown analyses in frequency domain, however, are affected by the artifacts from performing a Fourier transform. In this work, we investigate the impact of windowing ringdown signals to understand the importance of these effects for ringdown analyses with LIGO. We compare the impact of introducing high-frequency Fourier artifacts from sharply truncating the signal versus those which arise from smoothly tapering the signal while including contributions to the waveform from before the start of the ringdown. We find that including pre-ringdown waves has a larger impact on the ringdown SNR than the high-frequency artifacts do. We interpret the small effect of the high-frequency artifacts in terms of a correlation measure between the ringdown and the inspiral-merger waves for binaries with different total masses and mass ratios. We find the correlation is small in the cases that we considered.